The multi-level modulation system is employed, in particular in digital micro-wave communication. Heretofore, 2nQAM, such as BPSK, 4QAM, 16QAM, 32QAM, 64QAM, 128QAM, 256QAM and so forth have been used in the multi-level modulation.
In the digital micro-wave communication, BPSK, 4QAM, 16QAM, 32QAM, 64QAM, 128QAM, 256QAM and so forth have been used in general for circuit simplicity. However, with recent progress in the integrated circuit technology, implementation difficulties ascribable to circuit complexity are decreasing, while a demand for effective frequency utilization and effective transmission power utilization are becoming stronger.
For meeting this demand, various methods for constructing the multi-level modulation system, in which the number of the multi-level is not necessary 2n, have been proposed. Typical of these are “Multi-Level Modulation Demodulation Communication Method and System” as disclosed in the JP Patent Kokai Publication JP-A-04-196945, “Multi-Level Modulation Demodulation Device, Multi-Level Modulation Demodulation Communication System, Modulation Demodulation Program and Modulation Demodulation Method” as disclosed in the JP Patent Application No. 2001-246891, not laid open as of the filing time of the present application, and “Multi-Level Modulation Demodulation Device, Multi-Level Modulation Demodulation Communication System, Modulation Demodulation Program and Modulation Demodulation Method” as disclosed in the JP Patent Application No. 2001-246890, not laid open as of the filing time of the present invention.